Method for producing plasma flow, method for plasma processing, apparatus for producing plasma, and apparatus for plasma processing

ABSTRACT

Provided are a plasma stream generation method, a plasma processing method, a plasma generation apparatus, and a plasma processing apparatus using same, which enable plasma processing with rotating plasma to be controllably performed with stability and thereby improved in quality. The frequencies in four quadrants Z 1 -Z 4  are set at 7, 15, 6, and 20 Hz, respectively. This frequency variability can realize different rotational velocity of plasma in the four-portion partitioned rotational angle regions. The rotational velocities of plasmas P 2 , P 4  are greater than those of plasmas P 1 , P 3 . Thus, the rotating plasma, which rotates at a periodically varied rotational velocity as plasma P 1 , plasma P 2 , plasma P 3 , and plasma P 4  in that order while traveling in a circular orbit C, can be used for irradiation therewith, thereby performing uniform film formation treatment in first quadrant Z 1  to fourth quadrant Z 4.

FIELD OF THE INVENTION

The present invention concerns a plasma stream generation method, inwhich a supply source of a plasma constituent material is set up as acathode, an anode is arranged in front or circumference of said cathode,a plasma is generated by said anode surface by generation of an arcdischarge between said cathode and said anode, said anode is rotated,and thus a plasma stream is generated. Also, the present inventionconcerns a plasma processing method by said rotated plasma stream, aplasma generation apparatus that generates said plasma stream, and aplasma processing apparatus that does a plasma treatment such as filmformation by means of the plasma generated by said plasma generationapparatus.

BACKGROUND ART

Commonly, it is known that the solid surface characteristics areimproved by forming a thin film on or injecting ions into the surface ofa solid material in plasma. A film formed using plasma containing metalion or nonmetal ion strengthens the abrasion resistance/corrosionresistance of the solid surface, and it is useful as a protective film,an optical film, a transparent electroconductive film and such. Inparticular, a carbon film using carbon plasma has a high utility value,as diamond-like carbon film (denoted as “DLC”) formed from diamond andgraphite structures.

As a method for generating plasma containing metal or nonmetal ion,there is a vacuum arc plasma method. Vacuum arc plasma is formed in anarc discharge occurring between a cathode and an anode, where thecathode material evaporates from an existing cathode ray spot on thecathode surface, and it is plasma formed by this vaporized cathodematerial. Also, when a reactive gas is introduced as the ambient gas,the reactive gas is ionized simultaneously, too. An inert gas (denotedas “noble gas”) may be introduced along with said reactive gas, andalso, said inert gas can be introduced in place of said reactive gas. Bymeans of such plasma, a surface treatment can be done by thin filmformation or ion injection to a solid surface.

Normally, by vacuum arc discharge, from cathode spots, vacuum arc plasmaconstituent particles are is ejected, such as cathode material ions,electrons, and cathode material neutral atom groups (atoms andmolecules). At the same time, cathode material particles, referred to asdroplets, with size ranging from less than submicron and up to severalhundred microns (0.01-1000 μm), are also ejected. When these dropletsadhere to the surface of the object to be treated, the uniformity of thefilm formed on the surface of the object to be treated is lost, defectsof the thin film are caused, and an effect is caused on the surfacetreatment result of the film formation.

In a plasma processing apparatus using a vacuum arc plasma method, forexample, as present applicant already disclosed in Japanese PatentLaid-Open No. 2008-91184 bulletin (Patent Document 1), plasma isgenerated by inducing an electric spark between the cathode and thetrigger electrode, and generating a vacuum arc between the cathode andthe anode.

[Patent Document 1] Japanese Patent Laid-Open No. 2008-91184 bulletin

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In said plasma processing apparatus, as described in Patent Document 1,a deflection magnetic field is generated in the cross sectioncircumferential direction of the plasma transport tube path, so that itis applied to the vacuum arc plasma generated between the cathode andthe anode. Then, while rotating the plasma, it is made to travel throughthe plasma transport tube path, the rotating plasma beam is irradiatedto the object to be treated (work), and an efficient film formationtreatment is done without causing diffusion.

FIG. 10 shows schematically the beam configuration of vacuum arc plasma.As shown in this FIG. 10A), the beam cross section of plasma beam PBnormally is not a perfect circle, but instead it has a substantiallyelliptical cross section that is deformed, in which an imbalance occursin the plasma density profile. That is to say, the plasma densitydistribution, as shown in said FIG. 10B), is distributed so that it isspread in the direction of long axis Y, in comparison with the shortaxis X-direction. Therefore, when it is irradiated to work W, theirradiation area by the beam in the long-axis Y-direction becomes largerin comparison with the short-axis X-direction.

In the conventional rotation control of a plasma stream, a plasma streamthat rotates while describing a circular orbit is generated, and therotational velocity of the plasma is constant in all regions of therotation angle region of the plasma around the plasma travelingdirection. If the plasma density distribution can be assumed to have anormal distribution that is even toward both the X- and Y-directions, itshould be possible to do a film formation that is even along thecircumference, by the rotating plasma describing a constant-velocitycircular orbit. However, as discussed above, because there is animbalance in the plasma density profile, the quantity of the beamirradiation irradiated to the work varies along the circumference,causing an issue that the film thickness became uneven. The problem ofthis unevenness is explained in detail in the following.

FIG. 12 shows schematically the state of a conventional plasma rotation,in which a plasma beam is rotated with a constant velocity. The rotatingplasma shown in the figure rotates clockwise from plasma PB1 to PB2,PB3, and PB4, while describing circular orbit C. When each rotationangle region is compared in infinitesimal section ΔR of circular orbitC, because the irradiation time becomes constant in infinitesimalsection ΔR under the constant-velocity circular orbit, the thickness ofthe film formation varied greatly in the regions along the short-axisX-direction or the long-axis Y-direction, due to the imbalance in theplasma density distribution.

In FIG. 12, plasmas PB1 and PB3 are located in rotation angle regions inwhich the short-axis X-direction is placed on the orbit, and are inpositions that are 180° from each other, facing mutually. Plasmas PB2and PB4 are located in rotation angle regions in which the long-axisY-direction is placed on the orbit, and are in positions that are 180°from each other, facing mutually, and at the same time, deviate 90° fromplasma PB1 and PB3. When plasmas PB2 and PB4 are irradiated to the work,the amount of plasma irradiation is decided by the plasma densitydistribution that extends toward the long-axis Y-direction. On the otherhand, when plasmas PB1 and PB3 are irradiated to the work, the amount ofplasma irradiation is decided by the plasma density along the short-axisX-direction that is shorter than the long-axis Y-direction. Therefore,when the rotating plasma that rotates from plasma PB1 to PB2, PB3, PB4under a constant velocity while describing circular orbit C isirradiated, a clear difference in the film formation thickness occurredbetween plasmas PB1 and PB3, and plasmas PB2 and PB4. Of course, as awhole circular orbit C, an irregularity in the thickness at variouspoints of the film formation occurs, and a satisfactory plasma treatmentcould not be done. This irregularity in the film formation thicknessvaries by the effect of the unevenness in the plasma density profile,and because of this, a rotating plasma control itself for carrying out adesired plasma treatment became difficult.

The object of the invention, in view of said problem, is to provide aplasma stream generation method, a plasma processing method, a plasmageneration apparatus, and a plasma processing apparatus using it, inwhich plasma treatment by a rotating plasma is made stable andcontrollable, and thereby making it possible to improve the quality ofthe plasma treatment.

Means to Solve the Problems

The first form of the present invention is a plasma stream generationmethod, characterized in that a supply source of a plasma constituentmaterial is set up as a cathode, an anode is arranged in front orcircumference of said cathode, an arc plasma is generated between saidcathode and said anode by generation of an arc discharge, and a plasmastream is generated, rotating around a plasma traveling direction by arotation magnetic field, wherein a rotation angle region of plasmaaround said plasma traveling direction is partitioned into two or more,and a rotational velocity of plasma in respective rotation angle regionis made to be different.

The second form of the present invention is the plasma stream generationmethod according to the first form, wherein an X-direction magneticfield set up in a plasma distribution pathway is generated, aY-direction magnetic field perpendicular to said X-direction isgenerated, and said X-direction magnetic field and/or said Y-directionmagnetic field is varied according to said rotation angle region, thusvarying said rotational velocity of a plasma in said rotation angleregion, so that a plasma stream describing a circular orbit, anelliptical orbit, or a spiral orbit is generated.

The third form of the present invention is the plasma stream generationmethod according to the first or second form, wherein said rotationangle region is partitioned into 4n portions (n: positive integer).

The fourth form of the present invention is a plasma processing method,characterized in that a plasma treatment is done by supplying to anobject to be treated a plasma stream generated by said plasma streamgeneration method according to the first, second or third form.

The fifth form of the present invention is the plasma processing methodaccording to the fourth form, wherein when a film is formed on an innercircumference portion and an outer circumference portion of said objectto be treated, a plasma treatment is done by a plasma stream having arotation angle region in which said rotational velocity is different, sothat film thicknesses of said inner circumference portion and said outercircumference portion are made to become different.

The sixth form of the present invention is a plasma generationapparatus, characterized in that a supply source of a plasma constituentmaterial is set up as a cathode, an anode is arranged in front orcircumference of said cathode, an arc plasma is generated between saidcathode and said anode by generation of an arc discharge, and a plasmastream is rotated around a plasma traveling direction by a rotationmagnetic field, wherein a rotation angle region of plasma around saidplasma traveling direction is partitioned into two or more, and arotational velocity of plasma in respective rotation angle region ismade to be different.

The seventh form of the present invention is the plasma generationapparatus according to the sixth form, wherein said plasma generationapparatus comprises an X-direction magnetic field generating means thatgenerates an X-direction magnetic field set up in a plasma distributionpathway, and a Y-direction magnetic field generating means thatgenerates a Y-direction magnetic field perpendicular to saidX-direction, so that said X-direction magnetic field and/or saidY-direction magnetic field is varied according to said rotation angleregion, thus varying said rotational velocity of a plasma in saidrotation angle region, consequently generating a plasma streamdescribing a circular orbit, an elliptical orbit, or a spiral orbit.

The eighth form of the present invention is the plasma generationapparatus according to the sixth or seventh form, wherein said rotationangle region is partitioned into 4n portions (n: positive integer).

The ninth form of the present invention is a plasma processingapparatus, characterized in that said plasma processing apparatuscomprises said plasma generation apparatus according to the sixth,seventh or eighth form, a plasma transport tube that transports a plasmagenerated by said plasma generation apparatus, and a plasma processingportion that processes an object to be treated by said plasma suppliedfrom said plasma transport tube.

The tenth form of the present invention is the plasma processingapparatus according to the ninth form, wherein when a film is formed onan inner circumference portion and an outer circumference portion ofsaid object to be treated, film thicknesses of said inner circumferenceportion and said outer circumference portion are made to becomedifferent, by a plasma stream having a rotation angle region in whichsaid rotational velocity is different.

Effects of the Invention

The present invention, as a result of having studied said problemintensively, was done upon observing the fact that uniformization offilm growth cannot be achieved by a rotating plasma stream describing asimple constant-velocity circular orbit, due to an imbalance in theplasma density profile. That is to say, according to the first form ofthe present invention, a rotation angle region of plasma around saidplasma traveling direction is partitioned into two or more, and arotational velocity of plasma in respective rotation angle region ismade to be different. Because of this, in contrast with the conventionalconstant-velocity circular orbit (see FIG. 12), even if there is animbalance in the plasma density profile, it becomes possible to controlthe film formation treatment stably, by varying the plasma irradiationtime in the divided rotation angle regions. Thus, the quality of plasmatreatment can be improved.

According to the second form of the present invention, an X-directionmagnetic field set up in a plasma distribution pathway is generated, aY-direction magnetic field perpendicular to said X-direction isgenerated, and said X-direction magnetic field and/or said Y-directionmagnetic field is varied according to said rotation angle region, thusvarying said rotational velocity of a plasma in said rotation angleregion, so that a plasma stream describing a circular orbit, anelliptical orbit, or a spiral orbit is generated. Because of this, filmformation treatment using a desired plasma exposure configuration can bedone, depending on the irradiation condition of plasma.

According to the third form of the present invention, said rotationangle region is partitioned into 4n portions (n: positive integer).Because of this, by arranging, for example, a magnetic field generatingmeans that generates an X-direction magnetic field, together with aY-direction magnetic field perpendicular to the X-direction, in theouter circumference of the plasma distribution tube passage, therotational velocity of the plasma is made to be different in respectiverotation angle regions that has been partitioned into 4n (n: positiveinteger) portions. Therefore, a film formation treatment can becontrolled stably by varying the plasma exposure time in the multiplydivided rotation angle regions, even if there is an imbalance in theplasma density profile.

According to the fourth form of the present invention, a plasmatreatment is done by supplying to an object to be treated a plasmastream generated by the plasma stream generation method according to thefirst, second or third form. Because of this, by said plasma streamgeneration method, plasma can be irradiated onto said object to betreated as a rotating plasma stream in which the rotational velocity ineach rotation angle region is made to be different. This way, a plasmatreatment of superior quality can be done without producing anirregularity in the film formation thickness, by controlling the filmformation treatment stably.

In the present invention, the film formation treatment can be controlledstably, by varying the plasma exposure time in the multiply dividedrotation angle regions. Because of this, not only the film formationtreatment can be done homogeneously throughout the whole object to betreated, but also, even in the inner and outer circumferences of theobject to be treated, a plasma treatment can be done in one step, inwhich a desired difference in height is imparted precisely to the filmformation thickness, by varying the plasma exposure time. That is tosay, according to the fifth form of the present invention, when a filmis formed on an inner circumference portion and an outer circumferenceportion of said object to be treated, a plasma treatment is done by aplasma stream having a rotation angle region in which said rotationalvelocity is different, so that film thicknesses of said innercircumference portion and said outer circumference portion are made tobecome different. Because of this, for example, one may consider a casein which a medium for a hard disk drive is used as the object to betreated, and the film is formed more thickly at the load-unload zone atthe outer circumference side that requires durability higher than thedata zone at the inner circumference side. Previously, two steps wererequired, in which after a film is formed on the whole disc once,another film formation is done again at the outer circumference portionfor thickness. In contrast, by the single plasma treatment step, aplasma treatment can be done, in which a desired height difference isprovided in the film formation thicknesses at the inside and the outsidecircumferences, in high quality.

According to the sixth form of the present invention, a rotation angleregion of plasma around said plasma traveling direction is partitionedinto two or more, and a rotational velocity of plasma in respectiverotation angle region is made to be different. Because of this, even ifthere is an imbalance in the plasma density profile, it becomes possibleto control the film formation treatment stably, by varying the plasmairradiation time in the divided rotation angle regions. Thus, it becomespossible to provide plasma generating in which the quality of plasmatreatment can be improved.

According to the seventh form of the present invention, said plasmageneration apparatus comprises an X-direction magnetic field generatingmeans that generates an X-direction magnetic field set up in a plasmadistribution pathway, and a Y-direction magnetic field generating meansthat generates a Y-direction magnetic field perpendicular to saidX-direction, so that said X-direction magnetic field and/or saidY-direction magnetic field is varied according to said rotation angleregion, thus varying said rotational velocity of a plasma in saidrotation angle region, consequently generating a plasma streamdescribing a circular orbit, an elliptical orbit, or a spiral orbit.Because of this, it becomes possible to provide a plasma generationapparatus, in which film formation treatment using a desired plasmaexposure configuration can be done, depending on the irradiationcondition of plasma.

According to the eighth form of the present invention, said rotationangle region is partitioned into 4n portions (n: positive integer).Because of this, by arranging, for example, a magnetic field generatingmeans that generates an X-direction magnetic field, together with aY-direction magnetic field perpendicular to the X-direction, in theouter circumference of the plasma distribution tube passage, therotational velocity of the plasma is made to be different in respectiverotation angle regions that has been partitioned into 4n (n: positiveinteger) portions. Therefore, a plasma generation apparatus can berealized, in which it is possible to control stably a film formationtreatment by varying the plasma exposure time in the multiply dividedrotation angle regions, even if there is an imbalance in the plasmadensity profile.

According to the ninth form of the present invention, by the plasmageneration apparatus according to the sixth, seventh or eighth form, arotating plasma is generated, in which an irradiation time is varieddepending on multiply divided rotation angle regions, and film formationtreatment can be done by this rotating plasma supplied to said plasmaprocessing portion via said plasma transport tube. Because of this, aplasma treatment of superior quality can be done.

According to the tenth form of the present invention, when a film isformed on an inner circumference portion and an outer circumferenceportion of said object to be treated, film thicknesses of said innercircumference portion and said outer circumference portion are made tobecome different, by a plasma stream having a rotation angle region inwhich said rotational velocity is different. Because of this, forexample, one may consider a case in which a medium for a hard disk driveis used as the object to be treated, and the film is formed more thicklyat the load-unload zone at the outer circumference side that requiresdurability higher than the data zone at the inner circumference side.Previously, two steps were required, in which after a film is formed onthe whole disc once, another film formation is done again at the outercircumference portion for thickness. In contrast, by the single plasmatreatment step, a plasma treatment can be done, in which a desiredheight difference is provided in the film formation thicknesses at theinside and the outside circumferences, in high quality. Therefore, aplasma processing apparatus can be provided, in which such plasmatreatment can be done.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section outlined schematic diagram of a plasmaprocessing apparatus to which a plasma generation apparatus concerningan embodiment of the present invention has been installed.

FIG. 2 is a control block diagram of said plasma processing apparatus.

FIG. 3 is a figure showing a configuration of magnetic field generatorfor plasma rotation 37, and a rotation magnetic field generated bymagnetic field generator for plasma rotation 37.

FIG. 4 is an electric current control waveform diagram for describing asimple circle, and a circular Lissajous figure.

FIG. 5 is a pulse electric current waveform diagram of the presentembodiment, caused by a frequency variation.

FIG. 6 is a circular Lissajous figure by a four-fold partition of FIG.5.

FIG. 7 is a basic flow chart of a rotating plasma control concerning thepresent invention.

FIG. 8 is a waveform diagram of the pulse electric current for a spiralorbit, and a Lissajous figure of rotating plasma describing a spiralorbit.

FIG. 9 is a waveform diagram of the pulse electric current for adifferent spiral orbit, and a Lissajous figure of rotating plasmadescribing a spiral orbit.

FIG. 10 is a figure showing schematically the beam configuration ofvacuum arc plasma.

FIG. 11 is a figure for explaining a rotating plasma stream generated bymagnetic field generator for plasma rotation 37.

FIG. 12 is a figure showing schematically the state of a conventionalplasma rotation.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, the plasma generation apparatus and plasma processingapparatus concerning an embodiment of the present invention is explainedin detail based on the attached figures.

FIG. 1 is a cross section outlined schematic diagram of a plasmaprocessing apparatus to which plasma generation apparatus 1 concerningthe present invention has been installed. In plasma generating portion4, the supply source of a plasma constituent material set up as cathode(target) 2, and a tube-like anode 3 is set up at the front side ofcathode 2. In plasma generating portion 4, striker 5 of a triggerelectrode, arc power supply 11, cathode protector 12, and plasmastabilizing magnetic field generator (electromagnetic coil or magnet) 13are installed. Striker 5 is arranged freely rotatably, so that it canapproach toward and reverse from cathode 2. An electric spark isgenerated between cathode 2 and striker 5 under a vacuum atmosphere, avacuum arc is generated between cathode 2 and anode 3, and thus plasmais generated.

In the plasma processing apparatus concerning the present embodiment,plasma treatment is done by introducing rotating plasma stream generatedby the plasma stream generation method of the present invention intoplasma treatment chamber 28. Generation of said rotating plasma streamis done by introducing the plasma generated between cathode 2 and anode3 through plasma distribution pathway into discharge side radiallyreduced tube 27 positioned in the plasma stream entrance of plasmatreatment chamber 28, applying rotation magnetic field, and rotatingaround the plasma traveling direction. In this instance, the rotationangle region of the plasma around said plasma traveling direction ispartitioned into two sections or more by the rotation magnetic fieldcontrol. Thus, a rotating plasma stream is generated, in which therotational velocity of the plasma in respective rotation angle region isdifferent. It is introduced into plasma treatment chamber 28 towardplasma stream entrance shown by broken line C1. For the rotationconfiguration of the rotating plasma stream, a plasma stream describinga circular orbit, an elliptic orbit, or a spiral orbit can be generated,depending on the control of the rotation magnetic field, and therefore afilm formation treatment under an intended plasma exposure configurationcan be done, depending on the irradiation condition of the plasma.

Cathode 2 is the supply source of the plasma constituent material. Itsformation material is not limited in particular, as long as it is asolid having electroconductivity. An elemental metal, an alloy, anelemental inorganic substance, and/or an inorganic compound (metaloxide/nitride) can be used individually, or as a mixture of two kinds ormore. As for the formation material of anode 3, an electroconductivitymaterial that is a nonmagnetic substance and does not evaporate even atthe plasma temperature, can be used. By the vacuum arc discharge inplasma generating portion 4, vacuum arc plasma constituent particles,such as target material ion, electron, and cathode material neutralparticles (atoms and molecules), are ejected. Also, at the same time,cathode material particles (referred subsequently to as “droplets D”),whose size ranges from less than or equal to submicron and up to severalhundred microns (0.01-1000 μm), are also ejected. The generated plasmaadvances along plasma advancing path 6, is bent by angle θ towardconnecting advancing path 14 by means of a magnetic field formed bybending magnetic field generators 8, 8 in bending portion 7, andadvances toward connecting advancing path 14. At that instance, dropletsD are neutral electrically, and because they do not receive influence ofa magnetic field, they advance straightly along droplet advancing path9, and are collected to droplet collecting portion 10. In addition, inthe inner wall of each advancing path of droplet advancing path 9,baffles 15, 16, 17, 18, and 26 are installed, where droplets D collideand adhere. In addition, in the starting end side of plasma advancingpath 6, magnetic field generator 19 that generates a plasma advancingmagnetic field is set up.

Connecting advancing path 14 comprises a tube passage to which severalbaffles 16 have been installed on the inner wall, and it is connected toradially enlarged tube 21 that forms plasma advancing path 20.Connecting advancing path 14 includes introduction side radially reducedtube 22 connected to plasma introduction side starting end 21 a ofradially enlarged tube 21. Aperture for droplet capture 25 is installedat the step portion with introduction side radially reduced tube 22 atthe center of connecting advancing path 14. To the starting end side ofconnecting advancing path 14 and introduction side radially reduced tube22, magnetic field generators 23, 24 respectively are set up, forgenerating a plasma advancing magnetic field. Several baffles 26 areinstalled in the inner wall of introduction side radially reduced tube22.

In plasma discharge side finishing end 21 b of radially enlarged tube21, discharge side radially reduced tube 27 is connected. The outlet ofdischarge side radially reduced tube 27 is connected to plasma treatmentchamber (plasma treatment portion) 28, and to its connecting portion,aperture 31 is installed. To discharge side radially reduced tube 27,magnetic field generator 30 that generates a plasma advancing magneticfield, and magnetic field generator 37 for plasma rotation, are set up.In plasma treatment chamber 28, object to be treated 29 is set up at aposition where the plasma introduced from discharge side radiallyreduced tube 27 is irradiated.

Radially enlarged tube 21 comprises inner circumferential tube 32 andouter circumferential tube 33, and it is inclinedly arranged withrespect to introduction side radially reduced tube 22 and discharge sideradially reduced tube 27. Outer circumferential tube 33 does notparticipate in traveling of the plasma stream, but instead it is aprotection member of inner circumferential tube 32. Innercircumferential tube 32 is mounted in outer circumferential tube 33through an insulation material such as an insulating ring, and it isinsulated electrically from inner circumferential tube 32 and outercircumferential tube 33. Several baffles 17 are installed in the wallsurface of inner circumferential tube 32. In the outer circumference ofouter circumferential tube 33, straightly advancing magnetic fieldgenerator 36 generating a plasma advancing magnetic field is set up.Straightly advancing magnetic field generator 36 is composed of anelectromagnetic coil wound around the outer circumference of outercircumferential tube 33.

In FIG. 1, broken line A shows the traveling direction of the plasma.The plasma that has passed through connecting advancing path 14 passesthrough introduction side radially reduced tube 22, and advances insideradially enlarged tube 21 of plasma advancing path 20. At that instance,the remaining droplets D collide with and adhere to baffle 17, and areremoved. Furthermore, the plasma bends from plasma advancing path 20 andis introduced into discharge side radially reduced tube 27, and as shownby broken line C1, it is introduced into plasma treatment chamber 28through discharge side radially reduced tube 27.

The plasma stream introduced in radially enlarged tube 21 fromintroduction side radially reduced tube 14 is diffused by thediameter-enlarging effect of the plasma advancing path by radiallyenlarged tube 21. Because the droplets mixed with the plasma streamadvance straightly, they diffuse while colliding with the tube innerwall surface of radially enlarged tube 21 that has been inclinedlyarranged. By this diffusion, the droplets decrease in number at thecentral portion of the plasma stream, and it transitions to a state inwhich many droplets are distributed at the outer circumference of theplasma stream. By this change in distribution, the droplets collidetoward nearby step portions 34, 35 of radially enlarged tube 21 and theinner wall surface of inner circumferential tube 32, and are adhered andcollected. Furthermore, when they are discharged to discharge sideradially reduced tube 27 connected in a bent manner to plasma dischargeside finishing end 21 b, the droplets advancing straightly toward thedirection of arrow B collide with baffle 18, and are adhered andremoved.

To plasma treatment chamber 28, reactive gas is introduced as necessaryby a gas introduction system (not shown), and the reaction gas and theplasma stream are exhausted by a gas exhaust system (not shown). Inaddition, in the present embodiment, the plasma distribution pathway isformed by setting up a multiply bent advancing path between plasmagenerating portion 4 and plasma treatment chamber 28. However, thepresent invention is not limited to this, but it can be applied towardvarious plasma processing apparatuses having a substantially L-shapedadvancing path.

FIG. 2 shows a control block diagram of said plasma processingapparatus. In FIG. 2, mainly control circuits necessary for the plasmarotation concerning the present invention is shown, and a striker drivecontrol circuit, and a straightly advancing magnetic field controlcircuit, among others, are omitted. The control unit of the plasmaprocessing apparatus comprises programmable logic controller (PLC) 100.Touch panel display 101 is connected to PLC 100, and display output andsetting input are enabled by touch panel display 101. In PLC 100, aplasma rotation control program is stored, and pulse generator 103 isconnected, driven and controlled by this plasma rotation controlprogram. The pulsed output of pulse generator 103 go through DC servoamplifier 103 a, 103 b, and is directed toward oscillating magneticfield generator 37 a and oscillating magnetic field generator 37 b. Inaddition, direct current regulated power supply 102 is connected to PLC100, and the power output of direct current regulated power supply 102is directed toward straightly advancing magnetic field generator 30.

FIG. 3 shows the configuration of magnetic field generator for plasmarotation 37, and the rotation magnetic field generated by magnetic fieldgenerator for plasma rotation 37. Magnetic field generator 37 comprises,oscillating magnetic field generator 37 a that generates oscillatingmagnetic field B_(X) of the X-axis direction, and oscillating magneticfield generator 37 b that generates oscillating magnetic field B_(Y) ofthe Y-axis direction. These magnetic field generators are arranged sothat oscillating magnetic field B_(X) and oscillating magnetic fieldB_(Y) are perpendicular with respect to radially enlarged tube 21.Straightly advancing magnetic field B_(Z) of the Z-axis direction isformed by straightly advancing magnetic field generator 36. As aspecific example of a rotation magnetic field generating means of thepresent invention, a combination of oscillating magnetic field generator37 a and oscillating magnetic field generator 37 b is given, and therotation magnetic field comprises a synthetic magnetic field ofoscillating magnetic field B_(X) and oscillating magnetic field B_(Y).Oscillating magnetic field generator 37 a and oscillating magnetic fieldgenerator 37 b comprises an electromagnetic coil generating a deflectionmagnetic field (subsequently referred to as “deflection coil”). Inaddition, straightly advancing magnetic field generator 30 is composedof an electromagnetic coil wound around the outer circumference ofdischarge side radially reduced tube 27.

(3B) shows the relation between oscillating magnetic field B_(X)(t) attime t by oscillating magnetic field generator 37 a, oscillatingmagnetic field B_(Y)(t) at time t by oscillating magnetic fieldgenerator 37 b, and rotation magnetic field B_(R)(t) at time t. FIG. 3shows magnetic field applied to one location where the plasma stream inradially enlarged tube 21 passes, and straightly advancing magneticfield B_(Z) is made to be a steady magnetic field. The straightlyadvancing magnetic field can also be varied with time. Rotation magneticfield B_(R)(t₁) is synthesized from oscillating magnetic fieldsB_(X)(t₁) and B_(Y)(t₁) at time t=t₁.

As shown in (3B) and (3C) (description of time (t) is omitted),synthetic magnetic field B is synthesized from said rotation magneticfield B_(R) and straightly advancing magnetic field B_(Z). Saiddroplets-mixed plasma 9 is bent toward the direction of syntheticmagnetic field B, and advances through said discharge side radiallyreduced tube 27. Similarly, in (3A), rotation magnetic field B_(R)(t₂)is synthesized from oscillating magnetic fields B_(X)(t₂) and B_(Y)(t₂)at time t=t₂. That is to say, when time t advances from t₁ to t₂,oscillating magnetic fields B_(X)(t₁), B_(Y)(t₁) change to oscillatingmagnetic fields B_(X)(t₂), B_(Y)(t₂), and said rotation magnetic fieldB_(R)(t) rotates from B_(R)(t₁) to B_(R)(t₂). Therefore, by adjustingthe phase difference, frequency and amperage of the pulsed currenttoward oscillating magnetic field generators 37 a, 37 b, and controllingoscillating magnetic fields B_(X)(t), B_(Y)(t), a desired rotationmagnetic field B_(R)(t) can be generated. By the way, the time notation(t) is omitted subsequently, and the notation will be oscillatingmagnetic fields B_(X), B_(Y), and rotation magnetic field B_(R).

(3B) and (3C) shows the relation between oscillating magnetic fieldsB_(X), B_(Y), straightly advancing magnetic field B_(Z), rotationmagnetic field B_(R), and synthetic magnetic field B. In (3B), amplitudeB_(X0) of oscillating magnetic field B_(X) and amplitude B_(Y0) ofoscillating magnetic field B_(Y) are set to same value, and byoscillating magnetic fields B_(X), B_(Y) with 90° phase differenceoscillating at same frequency, rotation magnetic field B_(R) rotateswith a constant strength. Therefore, plasma stream 38 advances throughdischarge side radially reduced tube 27 while rotating in circle. In(3C), amplitude B_(Y0) is set to be smaller than amplitude B_(X0), andin the same manner as (3B), by making oscillating magnetic fields B_(X),B_(Y) with 90° phase difference oscillate in a same frequency, thevector of rotation magnetic field B_(R) in (3C) rotates in ellipticshape.

FIG. 11 schematically shows plasma stream 38 inside discharge sideradially reduced tube 27.

Plasma stream 38 inside discharge side radially reduced tube 27 curvesthrough the rotation effect of said rotation magnetic field B_(R), andwhile separating the droplets toward the direction of the wall sideshown by arrow 39, it become a rotating plasma stream, and advances tointroduction direction C1 toward plasma treatment chamber 28.

As shown in FIG. 2, the power control of oscillating magnetic fieldgenerator 37 a and oscillating magnetic field generator 37 b to theelectromagnetic coils is done individually by the current supply from DCservo amplifiers 103 a, 103 b that varies the energization quantity,based on the pulse signal generated by pulse generator 103. Pulsegenerator 103 generates pulse signal, as the plasma rotation controlprogram is executed by PLC 100. The control of the power from straightlyadvancing magnetic field generator 30 to the electromagnetic coil isdone by the power feed from direct current regulated power supply 102that is driven and controlled by PLC 100.

To each deflecting coil, sinusoidal current is supplied through DC servoamplifier 103 a, 103 b. Principle of plasma rotation control by feed ofsinusoidal current is easily explained in the following. When sinusoidalcurrent is expressed as Am sin 2π ft (Am: amplitude; f: frequency; t:time), the magnetic field formed by the deflecting coil when thissinusoidal current is conducted through the deflecting coil is zero atthe time of 2πf=nπ. At the time of 2πf=nπ/2s, it becomes 1 if n is anodd number, and −1 if it is an even number, and thus the direction ofthe magnetic field changes. As shown in (4A) of FIG. 4, for example,when a waveform electric current is supplied to each deflecting coil,and the waveform is sin 2πft and cos 2πft whose amplitudes are same butwhose phases are different, the plasma stream rotates so as to describea Lissajous figure of sin 2πft, cos 2πft, that is to say, a circle asshown in (4B) of FIG. 4. By the way, as already mentioned as a problem,if the plasma is rotated while frequency f is made uniform so that itdescribes a circular orbit, the rotational velocity of the plasmabecomes equal in all the regions among the rotation angle regions of theplasma around the plasma traveling direction.

In the present invention, it has been observed that the orbiting speedof the plasma is determined by frequency f of the pulsed current from DCservo amplifiers 103 a, 103 b. The rotation angle region of the plasmaaround the plasma traveling direction is partitioned into two or moreportions, and electric current control is done to make different therotational velocity of plasma in respective rotation angle region. Thisis done by partitioning said rotation angle region into 4n (n: positiveinteger) portions.

The present embodiment corresponds to a case in which the rotation angleregion is partitioned into four portions. FIG. 5 shows a pulse electriccurrent waveform diagram of the present embodiment, caused by afrequency variation. Respective frequency in the four quadrants Z1-Z4 isset to 7, 15, 6, 20 Hz. By this frequency variation setting, therotational velocity of plasma in the rotation angle region partitionedfour-fold can be made different. Previously, because in each quadrant,frequency f of the pulse current has been set to be a constant value,for example, 10 Hz, the rotational velocity of plasma was constant, asdiscussed above. However, according to the present embodiment, byvarying the plasma irradiation time in the partitioned rotation angleregions, the film formation treatment can be controlled stably even ifthere is a variation in the plasma density profile, and thus the qualityof the plasma treatment can be improved.

FIG. 6 shows the Lissajous figure from the four-fold partition of FIG.5. Although the plasma stream rotates so that it describes a circle, therotational velocities in the four quadrants Z1-Z4 are different. Inother words, the orbiting speed is slow in first quadrant Z1 and thirdquadrant Z3, and the orbiting speed is fast in second quadrant Z2 andfourth quadrant Z4. In FIG. 6, the fast orbiting speed in quadrants Z2,Z4 is illustrated by dot depiction.

In FIG. 6, P1-P4 shows the orbiting position in each quadrant of theplasma stream with variation in the plasma density profile. P1 and P3are located in the rotation angle regions where the shortened-axisX-direction is in the orbit, and are at locations where they face eachother in 180°. Plasma P2 and P4 are located in the rotation angle regionwhere there is an extended-axis Y-direction is in the orbit, face eachother at 180°, and, deviates 90° from plasma P1 and P3. When plasma P2and P4 are irradiated onto the work, the amount of the plasma exposureis determined by the plasma density profile that spreads along theextended axis Y-direction. On the other hand, when plasma P1 and P3 areirradiated onto the work, the amount of the plasma exposure isdetermined by the plasma density profile of the shortened-axisX-direction that is smaller than the extended-axis Y-direction. In thepresent embodiment, the orbiting speed of plasma P2 and P4 is fasterthan plasma P1 and P3. Because of this, by irradiating with the rotatingplasma that rotates periodically from plasma P1 to P2, P3, P4 whilevarying its velocity describing circular orbit C, a uniform film-formingprocess can be done in the range from first quadrant Z1 to fourthquadrant Z4. Within a whole circular orbit, an irregularity in thethickness at the film formation points does not occur, and asatisfactory plasma treatment can be done. Moreover, a control of therotating plasma for carrying out a desired plasma treatment, in which aneffect from an unevenness of the plasma density profile is not seen, anduneven spots in the film formation thickness are not formed, can be donesimply by means of frequency variation.

FIG. 7 is a basic flow chart of a rotating plasma control concerning thepresent invention. The control of the rotating plasma generationconcerning the present invention comprises PLC 100 and the executionprocess of frequency variation control executed by PLC 100. By an inputfrom the apparatus power supply (step ST1), a configuration settingtreatment of various parameters for the rotating plasma is done,preceding the plasma treatment (step ST2). The rotation controlparameter comprises frequency f and amplitude data. The amplitude datais necessary for later multiorbital control. If these various parametersare set, irradiation treatment of an object to be treated by therotating plasma becomes possible to carry out (step ST3).

If rotation control parameter is not set yet, setting of frequency f isdone (steps ST4, ST5). Upon setting frequency f, the frequency for eachrotation angle region is set according to the number of partitions 4n.In addition, one proceeds to configuration of the amplitude data, andaccording to the multiorbital control, the amplitude data is input andset (steps ST6, ST7). The setting of these various parameters can bedone by means of touch panel display 101.

In a conventional constant-velocity rotating plasma, as explained byFIG. 12, irregular spots of film formation thickness occurred in theobject to be treated. However, if the generation method of rotatingplasma concerning the present invention is used, an evenness of filmformation can be realized by doing rotating plasma control fordescribing multiple orbits. A rotating plasma describing multiple orbitscan be generated by changing with respect to time the amplitude of thepulse current supplied to each deflecting coil from DC servo amplifiers103 a, 103 b.

FIG. 8 is a waveform diagram of the pulse electric current for a spiralorbit, and a Lissajous figure of rotating plasma describing a spiralorbit. When the pulse current of the time variable amplitude isexpressed as sine wave Am(t)sin 2πft (Am(t): time-variable amplitude; f:frequency; t: time), the pulse currents of X-direction and Y-directionsupplied to respective deflecting coils become Ax(t)sin 2πft andAy(t)cos 2πft, respectively. (8A) of FIG. 8 shows one period of currentwave form Ax(t)sin 2πft, and a supply of pulsed current of this waveformis made repeatedly. A pulse current of Ay(t)cos 2πft is supplied as asimilar waveform, but with 90° phase difference. In the case of (8A),trace A1 of the amplitude peak values is approximated by at, and theamplitude varies linearly. Therefore, when a pulse supply of Ax(t)sin2πft and Ay(t)cos 2πft are done along with the frequency variablecontrol, a rotating plasma whose orbiting speed becomes different ineach rotation angle region, and furthermore, describes a spiral orbit,can be generated. That is to say, by means of the pulsed current supplywith time variable amplitude in (8A), as shown in Lissajous figure of(8B) in FIG. 8, a rotating plasma rotating in the inner and outercircumferences regularly in a given time period and describing a spiralorbit can be obtained.

FIG. 9 is a waveform diagram of the pulse electric current for adifferent spiral orbit, and a Lissajous figure of rotating plasmadescribing a spiral orbit. (9A) of FIG. 9, in a similar manner as (8A),shows one period of the current wave form of a sine wave, and supply ofpulsed current of this waveform is done repeatedly. In the case of (9A),trace A2 of the amplitude peak values is approximated by logs, and theamplitude is varied curvilinearly. Therefore, when the pulse supply ofsaid current wave forms Ax(t)sin 2πft, Ay(t)cos 2πft is done along withsaid frequency variable control, a rotating plasma can be generated, inwhich the orbiting speed differs according to the rotation angle region,and moreover, a spiral orbit different from the case in FIG. 8 isdescribed. That is to say, the rotating plasma in (8B) rotates withinthe spiral orbit around the inner and outer circumferences in a constanttime interval, but as shown in (9B), rotating plasma describing a spiralorbit that is dense in the outer circumference side can be obtained.When a rotating plasma describing said spiral orbit is used, it becomespossible to form a film, so that the film thicknesses are different atthe inner circumference and the outer circumference portions of anobject to be treated. For example, one may consider a case in which amedium for a hard disk drive is used as the object to be treated, andthe film is formed more thickly at the load-unload zone at the outercircumference side that requires durability higher than the data zone atthe inner circumference side. Previously, two steps were required, inwhich after a film is formed on the whole disc once, another filmformation is done again at the outer circumference portion forthickness. In contrast, by the single plasma treatment step, a plasmatreatment can be done, in which a desired height difference is providedin the film formation thicknesses at the inside and the outsidecircumferences, in high quality.

In addition, to vary the amplitude curvilinearly, the trace of theamplitude peak values may be approximated by exp(t).

The present invention is not limited to the embodiments described above.Various modifications, design alterations, and others that do notinvolve a departure from the technical concept of the present inventionare also included in the technical scope of the present invention.

INDUSTRIAL APPLICABILITY

According to the present invention, a control becomes possible of plasmatreatment using rotating plasma, and it contributes to an improvement inthe plasma treatment. Therefore, for example, it becomes possible toform homogeneously in plasma a film of high purity in which there are amarkedly few defects and impurities on the surface of a solid material,or reforming evenly in plasma the solid surface characteristics withoutadding defects and impurities. Therefore, a plasma processing apparatuscan be provided, in which an abrasion resistance/corrosion resistancereinforcement film, a protective film, an optical thin film, atransparent conductive film and such can be formed in high quality andprecision on a solid surface.

DENOTATION OF REFERENCE NUMERALS

-   -   1 Plasma generation apparatus    -   2 Cathode    -   3 Anode    -   4 Plasma generating portion    -   5 Striker    -   6 Plasma advancing path    -   7 Bending portion    -   8 Bending magnetic field generator    -   9 Droplet advancing path    -   10 Droplet collecting portion    -   11 Arc power supply    -   12 Cathode protector    -   13 Plasma stabilizing magnetic field generator    -   14 Connecting advancing path    -   15 Baffle    -   16 Baffle    -   17 Baffle    -   18 Baffle    -   19 Magnetic field generator    -   20 Plasma advancing path    -   21 Radially enlarged tube    -   21 a Starting end    -   21 b Starting end    -   22 Introduction side radially reduced tube    -   23 Magnetic field generator    -   24 Magnetic field generator    -   25 Aperture    -   26 Baffle    -   27 Discharge side radially reduced tube    -   28 Plasma treatment chamber    -   29 Object to be treated    -   30 Magnetic field generator    -   31 Aperture    -   32 Inner circumferential tube    -   33 Outer circumferential tube    -   34 Step portion    -   35 Step portion    -   36 Magnetic field generator    -   37 Magnetic field generator    -   38 Plasma stream    -   39 Arrow    -   100 PLC    -   101 Touch panel display    -   102 Stabilized DC power supply    -   103 Pulse generator    -   103 a DC servo amplifier    -   103 b DC servo amplifier

The invention claimed is:
 1. A plasma stream generation method,characterized in that a supply source of a plasma constituent materialis set up as a cathode, an anode is arranged in front or circumferenceof said cathode, an arc plasma is generated between said cathode andsaid anode by generation of an arc discharge, a plasma stream isgenerated by letting said arc plasma pass through a plasma distributionpathway, said plasma stream is made rotating around a plasma travelingdirection by a rotation magnetic field, where when an imbalance occursin a plasma density distribution along a beam cross section of saidplasma stream and said beam cross section is a deformed cross sectionhaving an extended-axis direction and a shortened-axis direction, anobject to be treated in a plasma treatment is irradiated with saidplasma stream being made rotating around said plasma travellingdirection while varying its rotational velocity describing a rotationalorbit, so that said plasma treatment is carried out while making a filmformation thickness uniform along said rotational orbit, and said plasmastream generation method comprises at least the steps of: (a)partitioning a whole circular rotation angle region of plasma aroundsaid plasma traveling direction into two or more; (b) setting afrequency for each divided rotation angle region; (c) executing afrequency variation control of rotating plasma generation, wherein saidfrequency in respective rotation angle region is made to be different,in such a manner that an orbiting speed of said plasma stream is slow ina rotation angle region where said shortened-axis direction is alongsaid rotational orbit, and an orbiting speed of said plasma stream isfast in a rotation angle region where said extended-axis direction isalong said rotational orbit.
 2. The plasma stream generation methodaccording to claim 1, wherein an X-direction magnetic field set up insaid plasma distribution pathway is generated, a Y-direction magneticfield perpendicular to said X-direction is generated, and saidX-direction magnetic field and/or said Y-direction magnetic field isvaried according to said rotation angle region, thus varying saidrotational velocity of a plasma stream in said rotation angle region, sothat a plasma stream describing a circular orbit, an elliptical orbit,or a spiral orbit is generated.
 3. The plasma stream generation methodaccording to claim 1 or 2, wherein said whole circular rotation angleregion is partitioned into 4n portions, wherein n is a positive integer.4. A plasma processing method, characterized in that a plasma treatmentis done by supplying to an object to be treated a plasma streamgenerated by said plasma stream generation method according to claim 1or
 2. 5. The plasma processing method according to claim 4, wherein whena film is formed on an inner circumference portion and an outercircumference portion of said object to be treated, a plasma treatmentis done by a plasma stream having a rotation angle region in which saidrotational velocity is varying, in such a manner that film thicknessesof said inner circumference portion and said outer circumference portionare made to become different.
 6. A plasma generation apparatus forgenerating a plasma stream, comprising: a supply source of a plasmaconstituent material being set up as a cathode; an anode being arrangedin front or circumference of said cathode; an arc plasma being generatedbetween said cathode and said anode by generation of an arc discharge;said plasma stream being generated by letting said arc plasma passthrough a plasma distribution pathway; said plasma stream being maderotating around a plasma traveling direction by a rotation magneticfield; a programmable logic controller; a setting input means forinputting and setting a rotation control parameter; said setting inputmeans being connected to said programmable logic controller: saidrotation control parameter including a frequency and amplitude data foreach rotation angle region when a whole circular rotation angle regionof plasma around said plasma traveling direction is partitioned into twoor more; and said programmable logic controller executing a frequencyvariation control of rotating plasma generation with said rotationcontrol parameter, where when an imbalance occurs in a plasma densitydistribution along a beam cross section of said plasma stream and saidbeam cross section is a deformed cross section having an extended-axisdirection and a shortened-axis direction, an object to be treated in aplasma treatment is irradiated with said plasma stream being maderotating around said plasma travelling direction while varying itsrotational velocity describing a rotational orbit, so that said plasmatreatment is carried out while making a film formation thickness uniformalong said rotational orbit, wherein said frequency variation control ofrotating plasma generation is executed in such a manner that saidfrequency in respective rotation angle region is made to be different,and that an orbiting speed of said plasma stream is slow in a rotationangle region where said shortened-axis direction is along saidrotational orbit, and an orbiting speed of said plasma stream is fast ina rotation angle region where said extended-axis direction is along saidrotational orbit.
 7. The plasma generation apparatus according to claim6, wherein said plasma generation apparatus comprises an X-directionmagnetic field generating means that generates an X-direction magneticfield set up in said plasma distribution pathway, and a Y-directionmagnetic field generating means that generates a Y-direction magneticfield perpendicular to said X-direction, so that said X-directionmagnetic field and/or said Y-direction magnetic field is variedaccording to said rotation angle region, thus varying said rotationalvelocity of a plasma stream in said rotation angle region, consequentlygenerating a plasma stream describing a circular orbit, an ellipticalorbit, or a spiral orbit.
 8. The plasma generation apparatus accordingto claim 6 or 7, wherein said whole circular rotation angle region ispartitioned into 4n portions, wherein n is a positive integer.
 9. Aplasma processing apparatus, comprising: said plasma generationapparatus according to claim 6 or 7, a plasma transport tube thattransports a plasma generated by said plasma generation apparatus, and aplasma processing portion that processes an object to be treated by saidplasma supplied from said plasma transport tube.
 10. A plasma processingapparatus comprising: said plasma generation apparatus according toclaim 7; a plasma transport tube that transports a plasma generated bysaid plasma generation apparatus; a plasma processing portion thatprocesses an object to be treated by said plasma supplied from saidplasma transport tube; and a means for changing with respect to timeamplitudes of pulse currents supplied to said X-direction magnetic fieldgenerating means and said Y-direction magnetic field generating means insuch a manner that when a film is formed on an inner circumferenceportion and an outer circumference portion of said object to be treated,film thicknesses of said inner circumference portion and said outercircumference portion are made to become different, by using said plasmastream having a rotation angle region in which said rotational velocityis varying.